SLIPPED CAPITAL FEMORAL EPIPHYSIS

CASE SUMMARY

Patient’s name : Soh Chee Roon

Age / Race / Sex : 11 years old / Malay / Boy

Orthopedic no. : 2866/ 02

The boy was referred to orthopedic clinic on 18th March 2002 by a general practitioner

with a presenting complaint of left groin pain for the past 3 months. The groin pain

was mild to moderate in severity especially on walking. He had a fall while running

prior to that. He had no similar problems in the past. There was no other pain

elsewhere.

On examination, he was obese. He was able to bear weight but with a limping gait. He

kept his leg externally rotated. There was a limitation of motion of his left hip

especially abduction and extension. There was one cm shortening of his left lower

limb.

A plain radiograph showed slipped capital femoral epiphysis grade 1of his left hip. A

Hip ultrasonography showed no joint effusion. He was referred to the Pediatric unit

for screening of endocrine abnormalities. The investigation result showed no

abnormality.

He underwent in situ single cannulated screw fixation of left hip on 25th March 2002.

He had preoperative skin traction of the affected limb for a few days prior to the

surgery.

The patient was positioned on a fracture table or radiolucent table in the supine

position to allow simultaneous biplane anteroposterior and lateral fluoroscopic

imaging. To determine the starting point, a guide-pin is placed on the skin overlying

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the proximal part of the femur and, under anteroposterior fluoroscopic guidance, the

pin is positioned such that it projects over the center of the femoral neck and head,

crossing the physis in a perpendicular fashion. Once this pin position has been

obtained, a marking pen is used to draw a line on the skin reflecting the pin position

on the anteroposterior image. The same procedure was used for the lateral

fluoroscopic image, and a two-centimeter skin incision is made at the intersection of

the two lines. The guide-pin is advanced freehand through the soft tissues to engage

the anterolateral femoral cortex. The position and angulation of the guide-pin are

adjusted, with fluoroscopic guidance, to obtain the proper alignment before the guide-

pin is drilled into the bone. It is ideal to advance the guide-pin into the center of the

femoral head, perpendicular to the physis, as seen on both the anteroposterior and the

lateral fluoroscopic images on the first attempt, since multiple drill-holes can weaken

the bone, causing a fracture through an unused hole. After the appropriate screw

length has been determined, a 7.3-millimeter stainless-steel cannulated screw is

placed over the guide-pin and is advanced until 5 threads engage the epiphysis. The

screw should not be left protruding beyond the lateral aspect of the femoral shaft,

where it can be toggled by the soft tissues, leading to screw loosening. After surgery,

the patient begins partial weight-bearing with use of crutches and gradually advances

to full weight-bearing as tolerated. Most patients can walk without crutches within

two to four days.

The pain resolved and his left hip range of motion was normal when he was followed

up 3 months postoperatively.

DISCUSSION

Slipped capital femoral epiphysis ( SCFE ) is a well known disorder of the hip in

adolescents that is characterized by displacement of the capital femoral epiphysis

from the metaphysis through the physis. The Incidence of SCFE is between 1-3:100

000 in the Caucasian and more in black population 7: 100 000. The boy is more

commonly affected as compared to girl with a ratio of 2-5: 1.The age of onset for

boys (13-15 years old) is much later than in girls (11-13 years old), which occur

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during the growth spurtThere is no local data to date regarding the prevalence of

SCFE in Malaysia.

The hip disorder should be suspected in a boy within the adolescent age group when

he presented with hip, thigh and knee pain.

The immediate etiology of slipping is mechanical. The femoral head or epiphysis is

held in the acetabulum by the ligamentum teres. The metaphysis in fact is one that

moves upward and outward while the epiphysis remains in the acetabulum. In most

patients, there is an apparent varus relationship between the head and the neck (the

epiphysis seem to be displaced posterior and inferior in relative to the neck of femur),

but occasionally the slip is into a valgus position. In the vast majority of cases, the

etiology is unknown / idiopathic. SCFE does not appear to be a heritable disorder. The

combination of both mechanical and biochemical factors have been proposed as the

etiology of idiopathic SCFE which may results in a weakened physis with subsequent

failure (Loder et al, 2000).

Mechanical factors associated with the disorder are obesity, increased femoral

retroversion and increased physeal obliquity (more vertical). Kitadai et al (1990) have

shown the association between children with SCFE and a deeper acetabulum (a mean

center-edge angle of Wiberg of 37 degrees compared with a mean of 33 degrees in

control subjects, a greater coverage of the femoral head yields more shear stress

across the physis). A 3 dimensional analysis based on computed tomography on

patients with SCFE by Kordelle et al (2001) revealed an association between the

disorder with reduced femoral anteversion and reduced femoral shaft neck angle.

However they found that SCFE has no influence on acetabulum development.

Biochemical factors are also likely involved. SCFE is a disease of puberty, when

many hormonal changes occur. The presences of perichondral ring and

transepiphyseal collagen fibers give strength to physis. The physis strength decreases

during period of growth spurt. The associated increased in physiological activity of

the physis and widening of the physis results in a rapid longitudinal growth in

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response to growth hormone. The effects of the gonadotropins on the physis may

explain the male predominance of SCFE; estrogen reduces physis width and increases

physis strength, whereas testosterone reduces physis strength. This probably explains

why the disorder is commoner in boys and extremely rare in girls after menarche. The

other hormonal disorders such, as excessive growth hormone secretion,

hypoparathyroidism, hypopituitarism and hypothyroidism may be associated with

SCFE (Loder et al, 2000).

An Idiopathic SCFE is the diagnosis made. There was no associated hormonal

imbalance / disorder found.

The Pathology of the disease is centered in the region of physis. The normal growth

plate is divided into a. the reserve or resting zone b. the proliferating zone c. the

maturity zone d. zone hypertrophic zone and e. the calcifying zone. Routine

histological evaluation and electron microscopy studies of SCFE demonstrated a

deficiency and abnormality in the supporting collagenous and proteoglycan

framework of the physis. Both the hypertrophic and the proliferative zones are

abnormal. Patient with SCFE has a widened physis region. The hypertrophic zone is

widened to 60-80 percent of growth plate as compared to 30 percent in normal person.

The plane of the slip passes through the different zone of physis and extending toward

the metaphysic. The physeal disruption leads to premature physis fusion, which,

usually occur in 1-2 years (Loder et al, 2000).

The Clinical Presentation varies with the type of slip. It can be divided into preslip

(6%), acute slip (11%), chronic slip (60%) and acute on chronic slip (23%).

Preslip: the child complains of some degree of groin and thigh pain especially

on prolonged standing or walking. It is associated with limitation of internal

rotation.

Acute slip: The pain present in less than three weeks duration with

demonstrable external rotation deformity, shortening, and marked limitation of

motion secondary to pain on physical examination. The child is unable to bear

weight.

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Chronic slip characterized by intermittent groin and thigh or knee pain for

several weeks or months. Physical examination usually demonstrates an

antalgic gait, limitation of flexion, internal rotation and abduction. The leg

usually externally rotated.

Acute on chronic slip patient sudden worsening of a chronic hip/ thigh / knee

pain.

The classification described above depends on the memory of the child or parent, or

both, and may be inaccurate; it also does not give a prognosis with regard to the

potential for avascular necrosis. Two newer and more clinically useful classifications,

one clinical and one radiographic, depend on physeal stability. Loder et al (1993)

divided SCFE into stable or unstable. The clinical classification depends on the ability

of the child to walk. The SCFE is considered stable when the child is able to walk

with or without crutches, and it is considered unstable when the child cannot walk

with or without crutches. The radiographic classification depends on the presence or

absence of a hip effusion on ultrasonography. If the ultrasound demonstrates the

absence of metaphyseal remodeling and the presence of an effusion, an acute event is

likely to have occurred and the SCFE is considered unstable. If the ultrasound

demonstrates metaphyseal remodeling and the absence of an effusion, an acute event

has not occurred and the slipped capital femoral epiphysis is considered stable.

Unstable slipped capital femoral epiphyses have a much higher prevalence of

avascular necrosis (up to 50 %in some series) compared with stable slipped capital

femoral epiphyses (nearly 0 percent). The high rates of complications with unstable

slips are most likely secondary to vascular injury caused at the time of the initial

displacement.

Considering the above discussion, the boy was having a chronic and stable slip type

of SCFE.

The Radiological Assessment should begin with a plain radiograph. An

anteroposterior (AP) and lateral frog position of the pelvis are usually

sufficient(Loder et al, 2000).

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On AP view:

The physis looks wider and irregular.

Trethowan’s sign (in English literature) or Klein’s line ( in the American

literature) signifies a line that is drawn along the superior border of the neck.

Normally the line passes through the head. In a slip, the line remains superior

to the head

In a gradual/ stable slip, there are radiographic signs of superior and anterior

remodeling on the femoral metaphysis and of periosteal new bone formation at

the epiphyseal-metaphyseal junction posteriorly and inferiorly.

The metaphyseal blanch sign of Steel is a double density seen at the level of

the metaphysis on an anteroposterior radiograph; the double density reflects

the posterior cortical lip of the epiphysis as it is beginning to slip posteriorly

and is radiographically superimposed on the metaphyseal density.

On lateral view:

The angle between the femoral neck to the epiphyseal base (epiphyseal-shaft angle as

described by Southwick) is normally 90° the on the frog-leg lateral radiograph. In a

slip, the angle decreases.

The degree of slippage is generally graded according the amount of the head

displacement in proportion to the width of the femoral neck on AP or Lateral view.

Preslip (Grade 1): There is a widening and rarefaction of the physis without

displacement.

Mild Slip (Grade II): The femoral head is displaced up to 1/3 of the femoral

neck on AP view or < 30° tilt on lateral view.

Moderate slip (Grade III): The femoral head slipped 1/3 to 2/3 of the femoral

neck on AP view or between 30°-50° tilt on lateral view.

Severe slip (Grade IV): The femoral head is displaced > 2/3 of the femoral

neck n AP view or > 50° tilt on lateral view.

A bone scan and a magnetic resonance imaging scan allow earlier diagnosis of

avascular necrosis and chondrolysis. An ultrasonography can be used to visualize an

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effusion in the hip (a sign of an unstable slipped capital femoral epiphysis) and

remodeling of the femoral neck (a sign of a stable slipped capital femoral epiphysis).

Two major issues arise when SCFE is left untreated. The head may slip further (as

long as the physis remained open) and the hip may develop early degenerative joint

disease in adult life. However, not many long term studies to date available to

associate the risk of developing early osteoarthrosis and SCFE. Hips with a severe

SCFE and those with avascular necrosis or chondrolysis undergo more rapid

deterioration with degenerative changes.

The most important priority in the treatment of a patient with a SCFE is to prevent

progression of the slip without causing additional harm (an avascular necrosis and

chondrolysis of the femoral head).

The current treatment methods for a patient with a stable (chronic) SCFE include:

1. immobilization in a hip-spica cast,

2. in situ stabilization with single or multiple pins or screws,

3. open epiphyseodesis with iliac crest or allogenic bone graft,

4. open reduction with a corrective osteotomy :

through the physis and internal fixation with use of multiple pins,

compensating base-of-neck osteotomy with in situ stabilization of the

slipped capital femoral epiphysis with use of multiple-pin fixation, and

intertrochanteric osteotomy with internal fixation.

(Loder etal, 2000)

The treatment in a hip spica should be considered as an alternative for patient with

stable SCFE. The hip spica avoids the complications associated with an operative

procedure. It is also provides prophylactic treatment of the contralateral hip. Betz et al

(1990) reported a high rate of complications following hip spica. The slip progressed

in two hips (5 percent) and chondrolysis developed in seven (19 percent. The hip-

spica cast is difficult to be maintained especially if the patient is obese. The use of hip

spica is not recommended.

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In Situ Stabilization with Use of Single cannulated screw in the center of the

epiphysis, perpendicular to the physis is preferable.

The blind spot, which is an area that cannot be visualized with the use of

anteroposterior and true lateral radiograph, is often the site of unrecognized pin

protrusion. Pin protrusion can be associated with the development of chondrolysis and

subchondral bone changes. With multiple pins, the possibility that one or more will

protrude into the joint is increased.

The results of single-screw fixation in patients with slipped capital femoral epiphysis

have been gratifying and a low prevalence of additional slippage and of

complications. Aronson and Carlson (1996) and Ward et al (1992) reported excellent

or good results in 95 percent and 92 percent, respectively, in patients with slipped

capital femoral epiphysis treated with single-screw fixation. A percutaneous in situ

fixation using two threaded Steinmann pins is associated with a high complication

rate (Blake et al, 1996). The complication includes progressive slippage; wound

infection one had a broken portion of pin during removal. There was no case of

implant failure and chondrolysis.

The most important contribution to the blood supply to the femoral head is from the

lateral epiphyseal vessels. The lateral epiphyseal vessels enter the femoral head in the

posterosuperior quadrant and anastomose with the vessels from the round ligament at

the junction of the medial and central thirds of the femoral head. The ideal position

for a screw, therefore, is in the central area or neutral zone of the femoral head. If a

pin is placed in the posterosuperior quadrant, the risk of damage to the epiphyseal

blood supply is increased

An open epiphyseodesis with Iliac cest or allogeneic bone graft is another option to

fuse the physis. The procedure avoids the complications associated with internal

fixation, including unrecognized pin protrusion, damage to the lateral epiphyseal

vessels, and hardware failure. The surgical technique involves an anterior iliofemoral

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exposure of the hip joint. A rectangular window of bone is removed from the anterior

aspect of the femoral neck. A hollow mill is used to create a cylindrical tunnel across

the physis, and multiple corticocancellous strips of iliac crest bone graft are driven

into the tunnel as bone pegs across the proximal femoral physis. However, the

fixation provided by the iliac crest bone graft is not as secure as that achieved by

internal fixation. Rao et al ( 1996) reported discouraging result with such procedure.

Complications such as progressive slip, an avascular necrosis and chondrolysis were

reported in significant number.

An open reduction with corrective osteotomy can be performed to correct the

deformity of femoral neck. The corrective osteotomy carries the risk of avascular

necrosis to the femoral head.

The prevalence of bilateral slipped capital femoral epiphysis has been reported to

range between 25 and 40 % in many series. However, recent studies with follow-up

into adulthood have demonstrated prevalence as high as 63 percent (Hurley et al,

1996). This wide range may be related to the variability in the radiological criteria

used to evaluate the hips, in the duration of follow-up, in the presence of symptoms in

the contralateral hip. The risk of developing a slip must be weighed against the risks

of an additional operation of a contra-lateral seems to be a normal side. Prophylaxis

pinning of the opposite hip may be considered in a high risk group of patient such as

obese child with endocrine abnormalities and a younger age boy at the time of initial

slip is predictive of contralateral slip (Stasikelis et al, 1996 ).

Two main complications may occur in SCFE.

1. Avascular necrosis: The risk of developing AVN is higher in unstable SCFE

as compared to stable SCFE which is rare.The factors responsible for the

development of AVN are:

an acute unstable SCFE

overreduction of an acute SCFE,

attempts at reduction of the chronic component of an acute-on-chronic

SCFE,

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placement of pins in the superolateral quadrant of the femoral head,

femoral neck osteotomy. The frequency of AVN is increased if a

cuneiform or basilar neck osteotomy is performed prior to physeal

2. Chondrolysis is defined as narrowing of the joint space to at least one-half of

that in the contralateral hip in unilateral cases and as narrowing of the joint

space to less than 3 mm in bilateral cases. The prevalence of chondrolysis in

patients with a SCFE is 5 to 7 percent. Risk factors leading to chondrolysis

include:

immobilization in a cast,

unrecognized permanent pin penetration,

severe SCFE, and

prolonged symptoms before treatment.

The treatment selected in this patient, in situ pinning was the best surgical option for

him as the case of chronic, stable SCFE. The patient has to be followed up regular

interval to detect a possibility of developing the contralateral slip and those

complications described above associated with in situ pinning of the affected hip.

CONCLUSION

The diagnosis of slipped capital femoral epiphysis should be ruled out in

adolescent presenting with hip/ thigh/ knee pain. Plain radiograph is usually sufficient

to make the diagnosis and grade the severity. Utmost importance is to classify the slip

whether it is stable or unstable. This simple classification has prognostic information

regarding the risk of developing avascular necrosis.

Regardless of the severity of the slip, in situ pinning provides the best long-term

function, the lowest risk of complications, and the most effective delay of

degenerative arthritis. Many patients with a slipped capital femoral epiphysis respond

well to this treatment, as seen at the time of long-term follow-up, if the slipped capital

femoral epiphysis is mild or moderate in severity, good congruity is maintained

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between the femoral head and the acetabulum, and avascular necrosis and

chondrolysis do not develop.

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